Faecal Calprotectin and 7-α Cholestenone Levels in Microscopic Colitis: Experience from Edinburgh

INTRODUCTION: Microscopic colitis (MC) is an important cause of chronic, watery diarrhoea. Currently, there is no specific biomarker available to guide diagnosis. The use of faecal calprotectin (FCP) as a potential marker has been addressed in only a few studies. Further, bile acid malabsorption (BAM) often accompanies MC. Current practice recommends the selenium-labelled homocholic acid-taurine (SeHCAT) test, but at our centre, 7 alpha-hydroxy-4-cholesten-3-one (7αC) is used as a simpler and less expensive alternative to SeHCAT, with values over 22ng/mL indicating BAM. This study aims to evaluate the use of FCP as a biomarker in the diagnosis of MC and the role of 7αC in detecting concomitant BAM with MC. METHODS: Pathology records were retrospectively reviewed for patients diagnosed with collagenous colitis (CC) between 2000 and 2018 and lymphocytic colitis (LC) between 1995 and 2011. FCP and 7αc results, if measured within 6 months of pathological diagnosis, were extracted for analysis. RESULTS: Between 2000 and 2018, 646 CC cases were confirmed on histology. Of 646 patients, 147 had FCP measured; in 111 (75.5%) FCP was elevated with mean levels 238.1μg/g (SD±273.0); 140/646 had 7αC measured; 16 (11.4%) indicated BAM. Mean levels were 10.2ng/mL (SD±9.4). During a 21-year period (1995–2011), 204 LC diagnoses were made: 14/204 had FCP measured; 8 (57.1%) were elevated. Mean levels were 128.4μg/g (SD±107.7). Of 204 LC patients, 20 had 7αC measured, 5 (25%) indicating BAM. Mean levels were 13.95ng/mL (SD±9.4). DISCUSSION: Both CC and LC were associated with raised FCP during the diagnostic phase, supporting the potential role of its use in clinical practice. Furthermore, we present results of using 7αC in identifying BAM amongst patients with MC. In our cohort, low levels of 7αC suggest relatively low concordance of BAM with MC.